This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Relay techniques have been intensively studied for the 3G/Beyond 3G/4G networks. A cell's coverage may be extended, for example to a further geographic reach or to provide coverage to areas which are ‘dead zones’ to the network base station, by using one or more Relay Nodes RNs to pass communications between the network base station BS and the end point user equipment UE. The relay nodes may be fixed or mobile, and some mobile relay nodes may be UEs which are not owned or operated by the radio network. For future wireless systems it is hoped that most if not all UEs can make themselves available from time to time for use as a mobile RN.
By employing advanced relaying techniques on the fixed and the movable RNs, the coverage area and/or the throughput of the networks could be enlarged. Compared with the fixed relay, the deployment for mobile relay deployment is much cheaper, faster and more flexible. For these reasons, mobile relay enhanced cellular networks is becoming a promising concept which has attracted more and more attention from both industry and academia.
Typically, in the prior art the relay selection is done for each relay link separately. The following three references illustrate that general prior art trend.                GB2346511 “COMMUNICATION SYSTEM USING MOBILE REPEATERS”. In this reference a cellular network finds a virtual routing path connecting BS and a certain UE via some MRs (Mobile Relays).        CN1984462A “WIRELESS NETWORK SYSTEM, ITS SWITCHING METHOD AND MOBILE STATION-TRANSFERRING EQUIPMENT”. This reference describes in a general way that terminals can access a BS via MR under a radio self-networking mode.        “APPROXIMATION ALGORITHMS FOR MULTI-POINT RELAY SELECTION IN MOBILE WIRELESS NETWORKS” (by Bernard Mans, Institut National de Recherche en Informatique et en Automatique, No 4925, September 2003; ISSN 0249-6399). This paper describes a source code that multiple neighbor nodes as its relay nodes (MPRs set) in order to find proper routing for a certain remote node (destination node). The inventors understand this paper to be an extension from a one-relay-node case as in reference GB2346511 to a multiple-relay-node case. In this paper, for every MPRs selection algorithm, the source node should know the set of its neighbors' neighbors, denoted as N^2(u). This then appears as a routing solution since the algorithm selects the MPR from knowledge of the source and destination nodes.        
A conventional scheme for pairing a MR to a Relay UE RUE is illustrated in FIG. 1. The term RUE is used to distinguish that particular UE which is the end-point of the relayed communication from other UEs which are not using a relay. FIG. 1 breaks the task of UE/MR role changing and MR-RUE pairing into five distinct steps each at different panels of FIG. 1. At panel 1 of FIG. 1 the RUE which is experiencing a bad channel sends some type of help request to the base station BS via some cellular uplink, which is a request for relay (if available).
At panel 2 of FIG. 1, once the BS successfully receives the help request from the RUE, the BS then: schedules some radio resource for RUE probing purposes; “wakes up” some IDLE user terminals such as via some paging channel and inform these terminals of the assigned resource for receiving the probing signal that the RUE will soon send (for clarity these user terminals A through D that have been awakened by the BS are termed here as MR candidates); and informs the RUE via downlink signaling of the assigned radio resource for sending the probing signal.
At panel 3 of FIG. 1 the RUE sends the probing signal over the assigned resource, and all the UEs (terminals A through D) which are willing to be a MR listen to the probing signal. At panel 4, all the MRs report the MR-RUE channel measurement results to the BS for a centralized decision for relaying. Then at panel 5 of FIG. 1 the BS makes the decision, based on the channel measurement reports, on which MR is to be paired with the RUE. The BS then informs the corresponding MR and the RUE of its pairing decision via downlink signaling. The pairing of the RUE in FIG. 1 is with MR terminal C which indicates a single hop relay.
Although the aforementioned conventional scheme gives a straightforward and feasible solution to UE/MR role changing and MR-RUE pairing, the inventors have identified the following issues:                RUE's “help” request does not reach the BS. In this case, such as for example if the RUE is located at “blind area” or too far away from the BS, the entire process of FIG. 1 cannot go forward.        Selection of MRs. Signaling all the UEs in the cell to receive RUE probing would be quite high signaling overhead, whereas if only a fixed number of UEs were selected randomly to be MR-candidates there is no guarantee that the channel between the RUE and any MR-candidate is good enough and so a successful pairing of RUE with MR cannot be assured with high probability. Choosing only those UEs that are close to the RUE as the MR-candidates means the BS must have fairly exact location/geography information of all the UEs (including UEs in IDLE mode), which would require GPS-equipped UEs report location information to the BS which also increases signaling overhead (and additionally geographic location does not always accurately reflect channel propagation in an urban environment where mobile RN use would be most likely).        MR candidate is unwilling. If for example the BS awakens five IDLE user terminals to be MR candidates in accordance with a RUE request, but three of them are unwilling to act as an MR (for example, due to low battery power), then the MR-RUE pairing procedure may fail when for example the remaining two MR candidates do not have a good enough channel quality with the RUE. In this case also the conventional scheme of FIG. 1 cannot assure a viable MR-RUE link even if the RUE finds a suitable MR candidate.        